1. Field of the Invention
The present invention relates to composite substrates and methods of producing composite substrates, in particular for use in the field of flexible electronics.
2. Description of the Related Technology
It is at least doubtful that the production of metallic conductors with low resistivity of e.g. 5 mΩ/square (meaning e.g. a Cu thickness of about 4 μm) onto a stretchable and/or flexible material (e.g. silicone) will be possible with an adhesion or a sufficiently good adhesion of the conductor to the stretchable and/or flexible substrate.
Solidifying overmould material may be used, resulting in a rigid plastic part with embedded conductors. In some cases a sacrificial layer may be used as a 70 μm thick Cu foil.
If the applied conductor pattern is a meander like structure (as shown for instance in “High-Conductivity Elastomeric Electronics”, Darren S. Gray et al., Advanced Materials 2004, 16, No. 5, March 5, p 393-p 397) it is believed that in this way thick (several microns) highly conductive (5 mΩ per square) fine pitch (40 μm or lower) stretchable conductors can be made.
The use of flexible and stretchable substrates and composite structures offer a lot of advantages when compared to rigid, not flexible and/or not stretchable substrates and structures, which are known to a person of ordinary skill. Various methods for producing stretchable electronic circuits have been mentioned (US patent application 2004 0243204 A1, and WO 2004 095536 A2=US 2004 0192082). R. Legge (U.S. Pat. No. 5,147,519) described a method of manufacturing elastomers containing fine line conductors. R. Legge uses a flat rigid material as sacrificial substrate.